New method for reconstructing satellite data

Researchers from the Center for Applied Space Technology and Microgravity (ZARM) at the University of Bremen and the German Aerospace Center (DLR) have developed a method for recovering faulty acceleration data from a satellite of the GRACE Follow-On mission. The failure of the acceleration sensor on one of the two satellites endangered the mission's goal of measuring the Earth's gravitational field with high accuracy. The team combined several data reconstruction approaches to improve the accuracy of simulated acceleration data for the faulty satellite.  

The GRACE Follow-On Mission, launched in May 2018, continues the important work of the previous GRACE project. Two satellites flying in close formation around the Earth continuously monitoring their distance to each other with high precision. The changing distance between the satellites then allows conclusions to be drawn about the Earth's gravitational field and its irregularities, providing information about changes in ice sheets and glaciers, underground water reservoirs, the amount of water in large lakes and rivers, as well as changes in sea level. About a month into the mission, the second satellite's accelerometer suddenly began producing faulty data. Alternative methods had to be developed to reconstruct the data for analysis of the Earth's gravity field, the mission's primary objective.

One promising solution was to transplant the acceleration data from the first satellite to the second. This transplantation method is based on the similar geometric shape and trajectory of both satellites. More specifically, an attempt was made to reconstruct the acceleration data of the second satellite using a simulation system called XHPS (eXtended Hybrid simulation Platform for Space systems). This program, developed by ZARM and DLR, allows precise calculations taking into account all environmental influences on the satellites geometry. However, this approach has reached its limits because each satellite has slightly different and therefore unique properties, despite having the same design.

Unfortunately, a comparison of simulated and real data also showed that the accuracy in the direction of flight needed to be improved due to the complex composition of the atmosphere. The research team developed an approach to improve the data in the direction of flight by estimating an atmospheric density that better matches the real conditions than the atmospheric model values.

The improved acceleration data from the second satellite now allows a more accurate determination of the Earth's gravitational field, contributing to the success of the GRACE FO mission.  Comparisons with data from institutes such as the Graz University of Technology and the NASA Jet Propulsion Laboratory also showed a high degree of congruence. The minimalist transplantation approach of the ZARM team, combined with high-precision environmental simulations, opens up new possibilities for space technology and research into the Earth's gravitational field.

The ZARM team now plans to further develop programs such as the XHPS and make them available to support future satellite missions. The publication ‘GRACE Follow-On accelerometer data recovery by high-precision environment modelling’ describes the successful work within the SFB 1464 TerraQ project B02.

Publication: https://doi.org/10.1016/j.asr.2024.03.068

Scientific contact person:
Moritz Huckfeldt
E-mail: moritz.huckfeldt(at)zarm.uni-bremen.de
Phone: 0421 218-57959

General press contact:
Jasmin Plättner
E-mail: jamin.plaettner(at)zarm.uni-bremen.de
Phone: 0421 218-57794